This invention relates in general to a mass transfer or distillation column and, more particularly, to a structure within the column for concurrently contacting a fluid stream with a particulate solid catalyst while distilling the reaction product.
The use of a catalyst packed distillation column allows concurrent catalytic reaction of a fluid stream flowing through the catalyst and fractionation of the resulting reaction product. The use of solid, particulate catalysts in a conventional fixed bed within such columns generally results in high pressure drop within the column as the low permeability of the catalyst bed impedes the upward flowing vapor and downward flowing liquid. Compaction and breakage of the catalyst in conventional fixed beds inevitably occurs and may further increase the pressure drop or may result in preferential channeling of the fluid streams through areas of high permeability. Portions of the catalyst bed having low permeability are then segregated from the fluid streams and the efficiency of the reaction process is reduced.
In an attempt to reduce the high pressure drop and channeling which may occur within the compact catalyst fixed bed, the particulate catalyst in some columns has been placed into a plurality of pockets within a cloth belt. The belt is then supported by a specially designed support structure such as an open mesh knitted stainless steel wire joined with the cloth belt. U.S. Pat. No. 4,242,530 provides an example of one such structure. While these types of reaction with distillation structures may provide reduced pressure drop and reduced- channeling within the distillation column, they often fail to achieve the distillation performance obtainable with many types of structured packings. Moreover, because the catalyst containers are intimately associated with the support structure, both the catalyst containers and support structure must be dismantled and replaced when the catalyst is spent. This can be a frequent occurrence when catalysts which have a cycle life as short as several months are used and results in significant losses in operating time.
Structured packings are also well known in the art including packings made of sheet material and having configurations for promoting vapor liquid contact. A particularly advantageous structured packing is that shown in U.S. Pat. No. 4,296,050. It has not heretofore been known to combine a structured packing of the type shown in the referenced patent with a fixed catalyst bed in a column where distillation and reaction occur simultaneously.